mq: copy pager attributes back to qrepo.ui
If the legacy pager extension is enabled, a pager is started through repo.ui
at dispatch._runcommand(). After that, mqcommand() creates a qrepo with a
fresh repo.baseui, at which point pager information was lost and another pager
would be spawned by the modern pager interface.
This is a minimal workaround for the problem.